## Doctoral Dissertations

Winter 1994

Dissertation

Chemistry

#### Degree Name

Doctor of Philosophy

Chifuru Noda

#### Abstract

This thesis presents vibrational overtone studies on N$\sb2$O, $\rm\sp{12}CO\sb2,$ OCS, and $\rm\sp{13}CO\sb2$ in the energy range from 10000 cm$\sp{-1}$ to 14000 cm$\sp{-1}$ by means of photoacoustic spectroscopy. Many new overtone and combination transitions have been discovered and some of the band intensities have been measured for the carbon dioxide molecule. The observed values of the transition positions and relative intensities are in good agreement with the theoretical calculations that were also performed. In addition, improvements on the experimental apparatus have been made during the investigations on these heavy-atom systems.

The text of this thesis is composed of seven chapters. The first one is an introduction which briefly describes the importance, the challenge of heavy-atom overtone spectroscopy and its relation to other research areas. The second chapter includes the general procedures of the experiments and descriptions of the main components of the apparatus. Chapter III depicts the improvements of the overall performance of the apparatus by introducing a new photoacoustic cell design.

The next three chapters contain the major portion of the thesis. Chapter IV presents the early studies on CO$\sb2$ and N$\sb2$O in the spectral range from 12500 to 14000 cm$\sp{-1}.$ One Fermi diad for CO$\sb2$ near 12700 cm$\sp{-1}$ and three bands for N$\sb2$O were observed. The absorption cross sections for these transitions were estimated. Chapter V contains the study of OCS in the spectral range from 10000 to 14000 cm$\sp{-1}.$ Fourteen overtone transitions have been discovered and assignments have been carried out for this molecule. Chapter VI describes the investigation of $\rm\sp{12}CO\sb2$ and $\rm\sp{13}CO\sb2$ in the same spectral as that for OCS. A total of twenty one overtone and combination transitions have been recorded and sixteen were observed for the first time. Analysis was performed by energy level calculations based on molecular parameters from literature. In addition, transition cross sections for the Venus bands are estimated.

Finally, the last chapter is the conclusion of this thesis. It presents the concluding remarks on what has been learned during the course of this thesis work and possible future research projects.

COinS